Traditional motor-driven compressor systems rely on a structural baseplate to locate and align the various components, including motors, compressors, gear boxes, etc. However, in some applications, for example, on off-shore oil platforms, space is at a premium; therefore, it is desirable to reduce the footprint of the compressor systems to the extent possible, without unacceptable sacrifices in efficiency, capacity, maintainability, or the like. As such, removal of supportive structural components would be desirable, so long as adequate rigidity and positional alignment of the various components could be maintained. As the baseplate typically provides this rigidity, it has generally not been considered an element that could be omitted from the system.
On the other hand, one way that the footprint of traditional systems has been reduced is by providing a motor that is configured to directly drive the compressor. This eliminates a need for a gear box, allowing a reduction in footprint size. Furthermore, some systems employ magnetic bearings, which eliminate the cost and complexity of traditional oil lubrication systems. Finally, some successful recent designs include an integrated, seal-less design where the motor and the compressor are housed in a single pressure containment vessel. The DATUM® C compressor, commercially-available from Dresser-Rand Company, Olean, N.Y., USA, is one example of such an integrated, seal-less compression system.
Although compact and suitable for a variety of applications, integrated compression system designs generally require significant specialization and customization at least of the motor, as the motor is required to interface with the compressor casing while maintaining a pressure barrier. Further, since the motor operates in the high-pressure environment of the compressor, motor efficiency drops can be experienced in comparison to atmospheric operation of the motor.
What is needed, then, is a compression system that has a reduced footprint, but obviates the above-described drawbacks experienced in integrated motor-compressor systems.